LogonUI.Exe Windows 7 won t start.

I can t login into my pc, the safe mode does work tho.
I get this error:
LogonUI.exe : The program can't start because SETUPAPI.dll
is missing from your computer. try re-installing
to fix the error.Anyone? Please this is urgent it s my office pc.
Answer #1
There’s a few things you could try:
1. Just copy the DLL from another Win7 PC (use a flash drive)
2. Use system restore (Start>All Programs>Accessories>System Tools>System restore)
3. Insert a Win7 disc, Click on the start menu and in the search box type cmd, Then right click it and pick “Run as administrator” (You may have to ask your boss/it admin for the password if prompted) then type the following
and hit enter:
sfc /scannow
and just wait for it to finish, It should copy back the file from the disc.
Answer #2
Just did sfc /scannow without the DVD disk, gonna resart nd check it out.
Edit: It didn t worked. Neither did under the boot DVD.
Edit2: Repair Install worked.